A Victorian coroner has recommended open-flue gas heaters be phased out following the death of a 62-year-old woman.

The coroner has investigated the death of 62-year-old Sonia Sofianopoulos, who died of carbon monoxide poisoning in her Melbourne unit in July 2017, due to a Vulcan Heritage heater.

Contractors employed by the Department of Health and Human Services (DHHS) had carried out non-compliant carbon monoxide testing in the unit two years before her death.

But Coroner Jacqui Hawkins found DHHS was only carrying out heater servicing every five years in about 70,000 residences instead of every two.

Still, she made no adverse findings against DHHS or the plumbing contractors.

Ms Sofianopoulos's death was found to have been the result of a confluence of events, including a carbon monoxide leak from the heater while at least one exhaust fan was on in her unit.

Open-flue gas heaters are only meant to be used in well ventilated spaces.

The coroner recommended regulations to prevent the sale of new open-flue heaters in Australia.

She also called for all gas fitters to undergo mandatory training as part of their licence.

Currently, plumbers and gasfitters are not required to keep their training up to date to remain registered.

Coroner Hawkins said the state regulator, Energy Safe Victoria (ESV), had not done its best to communicate changes in testing to gasfitters. ESV was found to have videos depicting the outdated testing regime on its website until just three months ago.

There are about 50,000 Vulcan Heritage or Pyrox heaters in Australia, among hundreds of thousands of other types of open-flue gas heaters.